dmaengine: bcm2835: Fix cyclic DMA period splitting

HiassofT · Vinod Koul · commit 2201ac6129fa · 2017-03-06T08:49:11.000+05:30
The code responsible for splitting periods into chunks that
can be handled by the DMA controller missed to update total_len,
the number of bytes processed in the current period, when there
are more chunks to follow.

Therefore total_len was stuck at 0 and the code didn't work at all.
This resulted in a wrong control block layout and audio issues because
the cyclic DMA callback wasn't executing on period boundaries.

Fix this by adding the missing total_len update.

Signed-off-by: Matthias Reichl &lt;hias@horus.com&gt;
Signed-off-by: Martin Sperl &lt;kernel@martin.sperl.org&gt;
Tested-by: Clive Messer &lt;clive.messer@digitaldreamtime.co.uk&gt;
Reviewed-by: Eric Anholt &lt;eric@anholt.net&gt;
Signed-off-by: Vinod Koul &lt;vinod.koul@intel.com&gt;
diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
@@ -251,8 +251,11 @@ static void bcm2835_dma_create_cb_set_length(
 	 */
 
 	/* have we filled in period_length yet? */
-	if (*total_len + control_block->length < period_len)
+	if (*total_len + control_block->length < period_len) {
+		/* update number of bytes in this period so far */
+		*total_len += control_block->length;
 		return;
+	}
 
 	/* calculate the length that remains to reach period_length */
 	control_block->length = period_len - *total_len;
